Unusual complexation of 1-phenylthiocarbamoyl-3-(pyridin-2-yl)pyrazoline with copper(ii) chloride

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2-Substituted imidazoles. 1. Reactions of 1-methyl-2-(2-furyl)imidazole with electrophiles

1-Methyl-2-(2-furyl)imidazole has been synthesized. Electrophilic attack (bromination, nitration, formylation, acylation, and hydroxymethylation) occurs in most cases at the free -position of the furan ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1396–1400, October, 1989.     

Synthesis and properties of 2-(2-furyl)-1-methyl-1H-acenaphtho[9,10-d]imidazole

2-(2-Furyl)-1-methyl-1H-acenaphtho[9,10-d]imidazole was obtained by the condensation of 9,1-acenaphthenequinone with furfural in the presence of ammonium acetate followed by N-methylation of the obtained 2-(2-furyl)-1H-acenaphtho[9,10-d]imidazole with methyl iodide in N-methylpyrrolid-2-one in the presence of potassium hydroxide. It was established that its electrophilic substitution in an acidic medium only takes place at position 2 of the furan ring while in a neutral medium both position 2 and position 7 of the aromatic part of the molecule undergo electrophilic attack. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 191–196, February, 2006.     

Photoisomerization of cis-1-(3-methyl-2-naphthyl)-2-phenylethene in glassy methylcyclohexane at 77 K

The cis-trans photoisomerizations of cis-1-(3-methyl-2-naphthyl)-2-phenylethene (c-3-MPE) was studied in methylcyclohexane (MCH) glass at 77 K. The fluorescence spectra of c- and t-3-MPE are excitation wavelength (λ(exc)) independent because the steric requirement of the methyl group restricts the conformational space of each isomer to a single conformer. Photocyclization, the dominant reaction pathway of c-3-MPE in solution, is entirely suppressed in MCH glass at 77 K. The only reaction on 313 nm irradiation of c-3-MPE in MCH glass is cis-trans isomerization. As the reaction progresses, the structureless fluorescence of c-3-MPE is replaced by the vibronically resolved fluorescence of the stable conformer of the trans isomer. The results are consistent with photoisomerization by the conventional one bond twist (OBT) pathway. Previously reported results on the photoisomerization of cis-1-(2-naphthyl)-2-(o-tolyl)ethene (c-NTE) are reinterpreted. Calculated geometries and energy differences for c- and t-3-MPE and c- and t-NTE [DFT using B3LYP/6-311+G(d,p)] are consistent with the interpretation of the experimental results.     

Zn(ii), Cd(ii) and Pb(ii) complexation with pyridinecarboxylate containing ligands

Herein, we report the coordination properties towards Zn(ii), Cd(ii) and Pb(ii) of two hexadentate ligands containing pyridinecarboxylate groups with ethane-1,2-diamine (bcpe) or cyclohexane-1,2-diamine (bcpc) backbones. The X-ray crystal structures of [Zn(bcpe)], [Cd(bcpe)] and [Cd(bcpc)] show hexadentate binding of the ligand to the metal ions, with the coordination polyhedron being best described as a severely distorted octahedron. The X-ray crystal structure of the Pb(ii) analogue shows the presence of tetrameric structural units [Pb(4)(bcpe)(4)] in which the four Pb(ii) ions are bridged by carboxylate oxygen atoms. While in the Zn(ii) and Cd(ii) complexes the bcpe ligand adopts a twist-wrap (tw) conformation in which the ligand wraps around the metal ion by twisting the pyridyl units relative to each other, for the Pb(ii) complex a twist-fold (tf) conformation, where a slight twisting of the pyridyl units is accompanied by an overall folding of the two pyridine units relative to each other is observed. Theoretical calculations performed at the DFT (B3LYP) level on the [Pb(bcpe)] and [Pb(bcpc)] systems indicate that the tf conformation is more stable than the tw form both in the solid state and in aqueous solution. The analysis of the natural bond orbitals (NBOs) indicate that the Pb(ii) lone-pair is polarized by a substantial 6p contribution, which results in a hemi-directed coordination geometry around the metal ion. Potentiometric studies have been carried out to determine the protonation constants of the ligands and the stability constants of the complexes with Zn(ii), Cd(ii), Pb(ii) and Ca(ii). The replacement of the ethylene backbone of bcpe by a cyclohexylene ring causes a very important increase in the stability constant of the Pb(ii) complex (ca. 2.3 logK units), while this effect is less important for Cd(ii) (ca. 1.4 logK units). However, the introduction of the cyclohexylene ring does not substantially affect the stability of the Zn(ii) and Ca(ii) complexes. The ligand bcpc shows Pb/Ca and Cd/Ca selectivities [10(8.9) and 10(9.8), respectively] superior to those of extracting agents, such as EDTA, already used in Pb(ii) and Cd(ii) removal from contaminated water and soils.     

Conversion of N-(1-oximino-1-phenylpropyl-2)-α-phenylnitrone into imidazole N-oxide derivatives

Treatment of N-(1-anti-oximino-1-phenylpropyl-2)--phenylnitrone with benzoic anhydride in benzene leads to simultaneous formation of benzoyl derivatives both of the corresponding nitrone and of 1-hydroxymethyl-2, 4-diphenyl-3-imidazoline-3-oxide. Treatment of the latter with hydrogen chloride led to the isolation of 5-methyl-2, 4-diphenylimidazol-3-oxide. Its isomer 4-methyl-2, 5-diphenylimidazol-3-oxide is formed by the action of HCl on syn and anti isomers of N-(1-oximino-1-phenylpropyl-2)--phenylnitrone. IR and UV spectra are used to determine the structures of the compounds, which are confirmed by synthesis.     

Azoimidazole Complexes of Manganese(II)-thiocyanate. X-ray Structures of 2-(p-tolylazo)imidazole and Bis-[1-methyl-2-(p-tolylazo)imidazole]- Di-thiocyanato-manganese(II)

The reaction of Mn(OAc)₂ · 4H₂O and 1-alkyl-2-(arylazo)imidazole [RaaiR′ where R = H (a), Me (b); R′ = Me (1/3/), Et (2/4/)] and NH₄NCS in MeOH in a 1:2:2 mole ratio afforded [Mn(RaaiR′)₂(NCS)₂] (3) and (4) complexes. They were characterized by different physicochemical methods and the structure has been confirmed by single crystal X-ray diffraction study for title compound. One of the primary ligands was also characterised by an X-ray diffraction study.     

Reaction of trans-dichloro-bis[N(1)-methyl-2-(arylazo)imidazole] ruthenium(II) with tertiary phosphines

Trans-dichloro-bis[N(1)-methyl-2-(arylazo)imidazol e] ruthenium(II) (tcc-Ru(MeL)2Cl2) reacts with tertiary phosphines giving rise to species of type [RuCl(P)-(MeL)2]+ and [Ru(P-P)(MeL)2]2+ in which Cl, P and P-P respectively occupy cis-positions [P=PPh3, or PPh2Me; P-P=Ph2P(CH2)2PPh2 (dppe) or Ph2P (CH2)3PPh2 (dppp)]. The cations have been isolated as perchlorates. The complexes display allowed t2(Ru) *(MeL) transitions in the visible region and show the energy ordering [RuCl(P)(MeL)2]+<[Ru(P-P) (MeL)2]2+. The RuIII/II couple occurs at high potentials, >1.1 V versus s.c.e. The azo reduction is sensitive to the nature of substituents in the ligand. The 1H n.m.r. spectra of the complexes are compatible with the isomer of C1-symmetry.     

Copper(II) complexation with 1-methyl-2-mercaptoimidazole in 7 M HCl

The complexation of copper(II) with 1-methyl-2-mercaptoimidazole in 7 M HCl was potentiometrically studied. The compositions of complexes were determined, and their stepwise formation constants were calculated. The complexes were shown to become less stable with increasing temperature. The thermodynamic functions of complexation were estimated. The copper complexes were shown to surpass the rhenium complexes in stability.     

Unusual result of the reaction of 4-(1-methyl-1H-imidazol-2-yl)methylene-substituted 2-alkylthioimidazol-5(4H)-one with copper(ii) chloride

A reaction of potassium ({(4Z)-4-[(1-methyl-1H-imidazol-2-yl)methylene]-5-oxo-1-phenyl-4,5-dihydro-1H-imidazol-2-yl}thio)acetate with copper(II) chloride in methanol leads to bis(5-anilino-7-methoxycarbonyl-1-methyl-1H-imidazo[1,2-c]pyrimidin-4-ium) tetrachloro-cuprate(II), whose structure was confirmed by the X-ray diffraction studies.     

Spectral study of complexation ofcis,cis-1,3,5-tri[2-(diphenylphosphinyl)ethylamino]cyclohexane with copper(ii) and cobalt(ii) ions

The complexation ofcis,cis-1,3,5-tri[2-(diphenylphosphinyl)ethylamino]cyclohexane (L¹) with Cu²⁺ and Co²⁺ cations has been studied in different solvents by means of UV-Vis, ESR, and IR spectroscopy. It has been shown that in the CuL¹ complex the metal ion is pentacoordinated by three nitrogen atoms and two phosphinyl groups of the ligand and has a tetragonal-pyramidal environment. The conformation of the coordination polyhedron for the CuL¹ complex depends on the solvent. In the CoL¹ complex, as well as in the CoL² complex, where L² is 1,4,7-tris(2-diphenylphosphinylethyl)-1,4,7-triazacyclononane, the Co²⁺ ion has an octahedral environment and is bound to all donor atoms of the ligands.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1199–1202, July, 1993.The authors are grateful to A. G. Matveeva and Yu. M. Polikarpov for the fruitful discussions.     

Synthesis and complexation behavior of N-(1-naphthylmethyl)-1,4,7,10,13-pentaoxa-16-azacyclooctadecane

A fluorescent photoinduced electron transfer (PET) sensor (3) that consists of 1-aza-18-crown-6 and a 1-naphthyl pendant shows a fluorescent increase with bivalent metal ions and a fluorescent decrease with monovalent metal ions. (1)H and (13)C NMR analyses of this 1:1 complexation behavior revealed that Ba(2+) strongly coordinates with the azacrown nitrogen to cause a dramatic decrease in the intramolecular charge-transfer character. In addition, it was suggested that not only the metal ion-dependent coordinated structure of the resulting complex but also the interaction between the thiocyanate anion and the naphthyl group play a role in controlling the extent of the emission-intensity increase and decrease that was observed in the presence of a given metal salt.     

Synthesis and spectral luminescence properties of 2-aryl-5-methyl-1,3,4-oxadiazoles and zinc(ii) 2-(2-hydroxyphenyl)-5-methyl-1,3,4-oxadiazole complex

Russian Chemical Bulletin - 2-Aryl-5-methyl-1,3,4-oxadiazoles were synthesized by reflux of equimolar amounts of acyl hydrazides with triethyl orthoacetate in o-xylene. The obtained oxadiazoles,...     

Adsorption of 2-(pyridin-2-yl)benzothiazoles with terminal thioacetate groups on the gold surface and their complexation with copper(ii) chloride

Russian Chemical Bulletin - A method for the preparation of new organic ligands combining in their structure a 2-(pyridin-2-yl)benzothiazole moiety capable of coordinating metal iones and a...